The European Court of Justice has rejected a crucial EU-US data sharing deal that could have serious ramifications for the relationship between Europe and Britain. Thejudges rejected the Privacy Shield agreement between the bloc and the USA. The tool is used by thousands of firms to protect Europeans’ personal data when it is transferred across the Atlantic. The agreement prompted complaints amid privacy concerns about the United States’ surveillance watchdogs. As part of the post-Brexit future relationship talks, the two sides want to establish an agreement to enable smooth flows of data after the transition period expires in December. The UK has fully rearranged the EU’s procedures into national law, but has a controversial track record in mass surveillance. In 2018 a European court ruled the UK had breached human rights protections in its mass surveillance programmes.